Long-term pot may damage gums but not lungs

People who smoke marijuana for up to 20 years have more gum disease, but otherwise don’t show worse physical health than non-smokers, a long-term study of nearly 1,000 New Zealanders from birth to age 38 finds.

Tobacco users in the study, which is published in JAMA Psychiatry, had gum disease as well as reduced lung function, systemic inflammation, and indicators of poorer metabolic health.

“We can see the physical health effects of tobacco smoking in this study, but we don’t see similar effects for cannabis smoking,” says lead author Madeline Meier, assistant professor of psychology at Arizona State University.

While study participants who had used marijuana to some degree over the last 20 years showed an increase in periodontal disease from age 26 to 38, they did not differ from non-users on any of the other physical health measures. To measure cannabis use, study subjects were asked to self-report their use at ages 18, 21, 26, 32, and 38.

The decline in periodontal health in pot smokers is not explained by tobacco smoking, alcohol abuse, or less tooth brushing and flossing. The lack of physical health problems among cannabis users also was not attributable to their having had better health to begin with or to living healthier lifestyles.

“We don’t want people to think, ‘Hey, marijuana can’t hurt me.’”

“We don’t want people to think, ‘Hey, marijuana can’t hurt me,’ because other studies on this same sample of New Zealanders have shown that marijuana use is associated with increased risk of psychotic illness, IQ decline, and downward socioeconomic mobility,” Meier says.

“What we’re seeing is that cannabis may be harmful in some respects, but possibly not in every way,” says coauthor Avshalom Caspi, professor of psychology and neuroscience at Duke University. “We need to recognize that heavy recreational cannabis use does have some adverse consequences, but overall damage to physical health is not apparent in this study.”

“Physicians should certainly explain to their patients that long-term marijuana use can put them at risk for losing some teeth,” says Terrie Moffitt, professor of psychology and neuroscience at Duke and co-director of the Dunedin Multidisciplinary Health and Development Study, from which these data were gathered.

Other researchers from Duke and from King’s College London and the University of Otago in New Zealand are coauthors of the study. The New Zealand Health Research Council, New Zealand MBIE, US National Institute of Aging, UK Medical Research Council, ESRC, and the Jacobs Foundation funded the work.